This invention relates to indicating instruments.
The invention is especially concerned with indicating instruments for use in assisting the pilot of an aircraft during the `ground-roll` phase of landing, that is, during the phase immediately after touchdown as the aircraft rolls along the runway.
It is desirable, especially during poor visibility conditions to provide the pilot of an aircraft with information concerning the speed of the aircraft along the runway, and also the length of runway remaining available for bringing the aircraft to a halt. From this information, the pilot can determine both his position along the runway, and whether or not he needs to increase the aircraft's rate of deceleration in order to stop within the available length of runway. With a known form of indicator used for displaying such information, the ground speed and remaining runway length is presented to the pilot in the form of analogue and digital displays respectively. Such an indicator suffers from the disadvantage that the pilot is required to carry out mental calculations from the information displayed on the distinct analogue and digital displays to determine whether his aircraft is going to stop in the available distance and to do so during an especially busy and dangerous period of the landing operation.